الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Ultra-wideband system is a candidate for high data rate short range wireless communication. It is based on the transmission of a train of ultra-short pulses which covers a huge bandwidth, the shorter the pulse duration, the larger its bandwidth. [t is suitable for being used with systems like PAN (Personal Area Network), WLAN (Wireless Local Area Network) and multimedia transmission systems. This would provide a very high data rate if not the FFC limitations. The FCC restricted the UWB system transmission, where the transmitter is permitted to transmit signal with very low power within the spectrum range 3.1-IO.6GHZ. The power limitation regularity reduced the probability of reception and detection of the transmitted signal at the receiver. The power constraint leads to degradation of the UWB systems performance, decrease in the data rate or transmission range, complication of the equipments and thus increasing their cost.
This dissertation proposes different receivers and system models to overcome the problems facing the UWB transmission. The first two contributions are two types of Rake receiver implementations which are applied to single-input single-output (S[SO), multi¬input single-output (M[SO) space time coding (STC), and multi-input multi-output (M[MO) STC UWB systems, to solve the problem of UWB performance degradation and/or decrease the receiver complexity. The first proposed Rake receiver is the adaptive GA (Genetic algorithm) Rake receiver. The adaptive Rake receiver uses Genetic algorithm (GA) to adaptively select the delays of the Rake receiver fingers depending on the channel impulse response and its strongest paths. The proposed GA Rake is used with space time coding to present a smart UWB system with better performance than the traditional UWB systems with low complexity receiver. This smart UWB system is modified by using a pre¬coding time reversal technique (TR) technique at the transmitter (TR smart UWB system). The modified smaJ1 UWB system introduces further progress in performance of the UWB system. The proposed TR smart UWB system also moves the complexity of the system from the receiver to the transmitter which decrease the overall cost and complexity of the system. The TR smart UWB system is also succeeded in combating interference from other UWB systems. The GA Rake in the smart UWB system succeeded to select the dominant path which represents the desired signal at the receiver and reject the interfering ones. This allows considering the TR smart UWB technique as a multiple access technique that can be used in multi user scenario. It can replace the conyentional multiple access techniques without inter-chip interference in multipath channel that degrades system performance. Another contribution of this dissertation is a type of Rake receivers, named the wavelet Rake (WR) receiver. The WR receiver uses the continuous wavelet transform of the transmitted pulse at different scales as the Rake fingers template pulses. The Rake fingers delays are taken as the group delays of the C[R corresponding to the template pulses center frequency. The WR does not only capture the signal energy in the different multi path components at different delays but also at different frecjuency components. The WR is able to decrease the complexity of the receiver and at the same time raise the reception and detection probability.
The last two contributions of the dissertation are two new wavelet based space time coding (STC) technique (WSTC), which are proposed to solve the data r’!te limitation problem. The proposed systems increase the data rate to four times the bit rate of a conventional space time coding system without increasing the bandwidth, symbol duration, or the bit energy. The first scheme WSTC-I based on multiplexing multiple symbols in the wavelet domain of the UWB pulses in addition to the spatial multiplexing offered by using multiple transmitting antennas. The WSTC-I uses Rake receivers and a combineI’ to collect the energy in the dense multipath channel components. The second scheme WSTC-I1 introduces a modification of the system model of WSTC-I to provide a less complex receiver with better performance. The WSTC-I1 like the WSTC-I provides frequency and spatial multiplexing in addition to introducing spatial diversity gain. The WSTC-I1 scheme introduces the same bit rate of the WSTC-I but with better performance and with less receiver complexity.
Simulations are presented using MATLAB software codes and performance is examined for different IEEE 802.15.3a line-of-sight (LOS) and NLOS indoor channel models.